U.S. patent number 4,864,562 [Application Number 07/134,081] was granted by the patent office on 1989-09-05 for sub-rate multi-media data transmission control system.
This patent grant is currently assigned to Mitsubishi Denki Kabushiki Kaisha. Invention is credited to Koh Kamizawa, Tokumichi Murakami.
United States Patent |
4,864,562 |
Murakami , et al. |
September 5, 1989 |
**Please see images for:
( Certificate of Correction ) ** |
Sub-rate multi-media data transmission control system
Abstract
A substrate multimedia data transmission control system in which
transmission frame bits set in a unit of a transmission frame
having a repeating cycle of 8 KHz according to the present
invention enables it to effect a realtime multiplexed bit
allocation in the 8 kbps unit in a variable fashion such that an
automatic matching of a transmission frame is achieved at an
initiation of a transmission and error check bits of the error
correction code are contained in a transmission frame with a
satisfactory matching. In addition, the multiframe configuration
according to the present invention enables it to handle in an
integrated fashion the synchronizations of the voice data frame,
the error correction frame, and the video data packet, which as a
result minimizes the size of the buffer memories disposed to send
and/or to receive motion video and which enables the transmission
speed smoothing operation to be accomplished in a simple
configuration through an easy control.
Inventors: |
Murakami; Tokumichi (Kanagawa,
JP), Kamizawa; Koh (Kanagawa, JP) |
Assignee: |
Mitsubishi Denki Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
17910689 |
Appl.
No.: |
07/134,081 |
Filed: |
December 17, 1987 |
Foreign Application Priority Data
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Dec 18, 1986 [JP] |
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61-302580 |
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Current U.S.
Class: |
370/538;
704/E19.003; 375/E7.277; 375/E7.275; 375/E7.279; 375/E7.271 |
Current CPC
Class: |
G10L
19/005 (20130101); H04J 3/1647 (20130101); H04N
7/54 (20130101); H04N 21/236 (20130101); H04N
19/89 (20141101); H04N 21/2383 (20130101) |
Current International
Class: |
G10L
19/00 (20060101); H04N 7/54 (20060101); H04N
7/60 (20060101); H04J 3/16 (20060101); H04N
7/64 (20060101); H04N 7/52 (20060101); H04J
003/22 () |
Field of
Search: |
;370/84,110.1,118,99 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
International Telegraph and Telephone Consultative Committee
(CCITT), Draft for Part 3 of Recommendation H.130, Jul. 1985, pp.
69-77. .
Robert M. Gray, "Vector Quantization", IEEE ASSP Magazine, Apr.
1984, pp. 4-29. .
Tokumichi Murakami et al., "Dynamic Multistage Vector Quantization
of Images", Electronics and Communications in Japan, Part 1, vol.
69, No. 3, 1986, pp. 93-101. .
T. Murakami et al., "Vector Quantizer of Video Signals",
Electronics Letters 11th, 1982, vol. 18, No. 23, pp.
1005-1006..
|
Primary Examiner: Olms; Douglas W.
Attorney, Agent or Firm: Bernard, Rothwell & Brown
Claims
What is claimed is:
1. A sub-rate, multi-media data transmission control system in
which multi-media data series, including motion video data, voice
data, and external digital data are multiplexed and transmitted
through a transmission line having a maximum transmission speed of
64 kbps.times.N.sub.1, N.sub.1 being an integer at least equal to
one, at a variable speed of 64 kbps.times.N.sub.2, N.sub.1
.gtoreq.N.sub.2 .gtoreq.1, comprising:
means for setting a basic transmission frame to N.sub.1 .times.8
bits at a frequency of 8 kHz in which a subframe of N.sub.2
.times.8 bits is used at said variable speed of 64
kbps.times.N.sub.2 with a dummy subframe of (N.sub.1
-N.sub.2).times.8 bits;
multiplexing means for multiplexing said multi-media data series
into said transmission frame by allocating 1/8 bits for each data
type of said series in said transmission frame, wherein 1 is the
transmission speed of each data type in kbps;
transmission speed matching means for setting the number of data
bits in a transmission frame to 8 bits.times.N.sub.1 for a
transmission speed of 64 kbps.times.N.sub.1, and to 8
bits.times.N.sub.2 for a transmission speed of 64
kbps.times.N.sub.2, forming a multiframe of J transmission framed
divided into even and odd numbered frames, J being an integer at
least greater than one, and assigning particular frame
synchronization data, transmission speed/bit allocation data and
control data to a particular bit in each frame of said multiframe
in a timesharing fashion thus establishing a frame/multiframe
synchronization autonomously matching the transmission speed;
frame synchronization means for setting an integral ratio between
the number of bits of voice data allocated in a multiframe and the
length of a voice data transmission frame to establish an
integrated frame synchronization with respect to synchronization of
said transmission frame;
correction encoding means for performing error correction encoding
on predetermined bits in a unit of said multiframe;
identification information adding means for subdividing said video
data into each unit of said error correction encoding operation and
adding information thereto identifying the type of motion video
data contained therein; and
transmitting means for transmitting multiplexed information
attained from said multiplexing means at intervals of K multiframes
in a real time fashion, K being an integer at least equal to
one.
2. A system in accordance with claim 1 wherein said correction
encoding means effects an error correction encoding by use of
Bose-Chaudhuri-Hocquenghem (BCH) code as an error correction code,
said code matching with a bit length of said multiframe so as to
arrange error correction bits of said BCH code at predetermined bit
positions of said frame bits, thereby achieving the error
correction encoding only on said motion video data.
3. A system in accordance with claim 1 wherein said correction
encoding means adds information identifying an invalid data
contained in the motion video data obtained through the subdivision
in the error correction encoding unit and motion video data types
including a first item, an intermediate item, and a last item of
the video frame to transmission data and transmits a resultant
transmission data therefrom.
4. A system in accordance with claim 1 wherein only in a case where
said digital data is transmitted in a predetermined period of
successive time during an ordinary transmission, a transmission
speed of an integral multiple of 8 kbps is allocated for a
transmission according to a predetermined procedure, and in the
other cases, the transmission speed is allocated to the video
data.
5. A system in accordance with claim 1 wherein said identification
information adding means effects a voice activation, in case the
multiframe is set to an integral multiple of the voice data frame,
to identify an interval with a voice and an interval without a
voice in a unit of k multiframes, transmits only a voice data frame
associated with the interval with a voice, and employs a control
increasing the allocation to the voice data in case of the interval
without a voice, which is identified depending on bit allocation
information in said frame bits in a unit of said k multiframes.
6. A system in accordance with claim 1 wherein when said
transmission line has a transmission speed of 64 kbps.times.2=128
kbps at the maximum and is capable of a variable-transmission-speed
connection for 64/128 kbps, the bits speed is fixed to 128 kbps,
the transmission frame length is fixed to 16 bits, all 16 bits of
said transmission frame are utilized for a 128 kbps operation,
eight bits of said transmission frame are used for a 64 kbps
operation, the frame bit of said transmission frame is set to one
bit, and the multiframe configuration includes 80 frames.
7. A system in accordance with claim 1 wherein said correction
encoding means utilizes as an error correction code a (320, 302, 5)
shortened BCH code, a (640, 620, 5) shortened BCH code, or a (1280,
1258, 5) shortened BCH code so as to establish a matching with said
multiframe including 80 frames.
8. A system in accordance with claim 1 wherein said transmission
speed matching means sets the voice data frame to 160 bits for an 8
kbps operation and to 320 bits for a 16 kbps operation so as to
match said voice data frame with a cycle of said multiframe
including 80 frames.
9. A system in accordance with claim 6 wherein said correction
encoding means utilizes as an error correction code a (320, 302, 5)
shortened BCH code, a (640, 620, 5) shortened BCH code, or a (1280,
1258, 5) shortened BCH code so as to establish a matching with said
multiframe including 80 frames.
10. A system in accordance with claim 6 wherein said transmission
speed matching means sets the voice data frame to 160 bits for an 8
kbps operation and to 320 bits for a 16 kbps operation so as to
match said voice data frame with a cycle of said multiframe
including 80 frames.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sub-rate multi-media data
transmission control system for transmitting information such as a
motion video, a voice, and data at a sub-rate.
2. Description of the Prior Art
FIG. 8 is a diagram schematically showing a configuration example
of a transmitter according to the conventional sub-rate multi-media
data transmission system described, for example, in the CCITT Draft
Recommendations H.130 Part 3 in which the configuration includes a
motion video encoder 1, a transmission buffer 2 for interfacing or
matching the code transmission speed with the encoded output
delivered from the moving picture encoder 1 of which the amount of
the encode data is not uniform, a video image frame data 3 read
from the transmission buffer memory 2 at a code transmission speed,
an error correction encoder 4 for effecting a (255, 239, 5) BCH
encoding operation on the video image frame data 3, an error
correction frame data 5 outputted from the error correction encoder
4, a 16-phase interleaver 6 for achieving a 16-phase interleaving
operation on the error correction frame data 5, video image data 7
delivered from the 16-phase interleaver 6, a voice encoder 8, voice
data 9 transmitted from the voice encoder 8 at a speed of 64 kbps,
digital data 10 having various speeds, an external data
multiplexing section 11 for multiplexing the digital data 10 with a
speed conversion so as to transmit the data at a speed of 64 kbps,
external data 12 sent from the external data multiplexing section
11 at a speed of 64 kbps, a control section 13 between apparatuses
which effects a communication control with communicating
apparatuses, control data 14 outputted from the control section 13
at a speed of 32 kbps, a multiplexed control signal 15 delivered
from the control section 13, a multiplexing section 16 for
multiplexing the video data 7, the voice data 9, the external data
12, and the control data 14 so as to send these data at a speed of
1.544 Mbps, and a transmission frame 17 sent from the multiplexing
section 16 at a speed of 1.544 Mbps.
FIG. 9 is a schematic diagram illustrating a transmission frame
configuration of the transmission apparatus of FIG. 8 according to
the conventional sub-rate multi-media data transmission control
system. The configuration includes transmission data 17 at a speed
of 1.544 Mbps in which a transmission frame comprises 193 bits, a
transmission frame bit F.sub.r 20 assigned to each transmission
frame of the transmission data 17 and the use of which is repeated
at an interval of 24 transmission frames, an odd-numbered frame 21
obtained by classifying the transmission data 17 into odd-numbered
frames and even-numbered frames respectively, and similarly an
even-numbered frame 22 thereof.
FIG. 10 is a schematic diagram showing a process in which the
motion video data 3 is encoded for a transmission path in the
transmission apparatus of FIG. 8 according to the conventional
sub-rate multi-media data transmission control system. The
configuration comprises a unique code word 30 indicating the top of
a video image frame, encoded data of the first block line 31
located at the uppermost end of a screen when a video frame is
structured in the screen in which a block line includes several
lines in the horizontal direction and the block line is assigned as
the minimum encoding unit, encoded data of the second block line 32
formed in the similar fashion, encoded data of the n-th block line
(n is an integer at least equal to one) 33 similarly located at the
lowermost end of the screen, 256-bit error correction frame data 5
which is obtained by effecting the (255, 239, 5) BCH encoding on a
239-bit unit data beginning from an arbitrary position of the video
image data and thereafter by adding an error correction frame bit
34, an error correction frame bit S which identifies a division
point of the 16-phase interleave and a division point of the error
correction frame and of which the utilization is repeated at an
interval of 16 error correction frames, an information bit 35 of
the 239-bit (255, 239, 5) BCH code obtained by dividing the image
data 3 at an arbitrary position, a 16-bit error correction code Ecc
36 added to the information bit 35, transmission video image data 7
attained by effecting a 16-phase interleaving on the error
correction frame 5, and data 38 obtained by achieving the 16-phase
interleaving on the error correction frame 5 excepting the error
correction frame bit S.
Next, the operation of the configuration above will be described.
The encoded output resulting from the encoding operation of the
motion video encoder 1 is temporarily stored in the transmission
buffer memory 2 and thereafter is read therefrom at a code
transmission speed, thereby matching the encode speed with the code
transmission speed. The video image data 3 read from the
transmission buffer 2 is inputted to the error correction encoder
4, which effects the (255, 239, 5) BCH encoding on the data to
attain the error correction frame data 5. Next, the video data 7
having undergone the 16-phase interleave operation in the 16-phase
interleaver 6 is sent to the multiplexer 16 so as to be multiplexed
into transmission data at a speed of 1.544 Mbps. On the other hand,
the voice data 9 encoded by the voice encoder 8 is fed to the
multiplexing section 16 at a speed of 64 kbps. The digital data 10
at various speeds, for example, 1200 bps and 2400 bps data is
multiplexed by the external multiplexing section 11 according to
the procedure described in, for example, the CCITT Recommendations
X.50 into the external data 12 at a speed of 64 kbps and is then
delivered to the multiplexer 16. In the controller 13 between
apparatuses, information necessary to be sent to a communicating
apparatus for the communication control with the communicating
apparatus is delivered as control data to the multiplexer 16 at a
speed of 32 kbps.
In the multiplexing section 16, the video data 7, the voice data 9,
the external data 12, and the control data are multiplexed into a
transmission frame 17 at a speed of 1.544 Mbps according to the
predetermined frame configuration indicated by the multiplex
control signal 15 sent from the controller 13 between apparatuses,
thereby transmitting the multiplexed data to a transmission
line.
Next, referring to FIG. 9, description will be given of the
transmission frame configuration. According to the CCITT Draft
Recommendations H.130 Part 3, the transmission is accomplished at a
transmission rate of a so-called Primary Group (1.544 Mpbs) and a
transmission frame 17 includes 193 bits; consequently, the frame
repeat cycle is obtained as 1.544 Mbps/193 bits=8 kHz. Assume that
bit 0 of the transmission frame 17 is a frame bit F.sub.r 20 and
that the remaining 192 bits ranging from bit 1 to bit 193 are
assigned to an information channel. The utilization of the frame
bit F.sub.r 20 is repeated for each 24 frames according to the
CCITT Recommendations G.704 and information such as the frame
synchronization, the multiframe synchronization, the data link, and
the CRC-6 are subjected to a time-sharing operation. The
information bits of a transmission frame 17 are subdivided into
items TS1-TS.gtoreq.each comprising 8 bits, and the multi-media
data is multiplexed according to this unit.
First, the 24 multiframes are classified into odd-numbered frames
21 and even-numbered frames 22, TS1 and TS16 are respectively
assigned to the voice data 9 and the external data 12, and TS2 of
the odd-numbered frame 21 is assigned to the control data 14. The
TS other than those above are assigned to the video image data 7.
As a result, the multiplexing rate of each data becomes as
follows.
Frame bit F.sub.r 20: 1 bit.times.8 KHz=8 Kbps
Voice data 9: 8 bits.times.8 KHz=64 Kbps
External data 12: 8 bits.times.8 KHz=64 Kbps
Control data 14: 8 bits.times.8 KHz 1/2=32 Kbps
Video data 7: 1.376 Mbps
In general, the bit synchronization and the 8-bit octet
synchronization must be retained for the 64 Kbps voice data. In
this case, however, the octet synchronization is established based
on a fact that the data is multiplexed in the transmission frame 17
in a unit of eight bits.
For the external data 12, a frame pattern conforming to, for
example, the CCITT Recommendations X.50 is inserted into the
external data channel TS16 thereof so as to establish the frame
synchronization independent of the synchronization of the
transmission frame 17.
For the motion video data 7, since the required bits error rate
thereof is critical in general as compared with the error rate of
the ordinary transmission path, the transmission path error
countermeasurement is effected through the (255, 239, 5) BCH
encoding and the 16-phase interleaving operation. Consequently, the
start bit of the 16-phase interleaving and the start bit of the
(255, 239, 5) BCH are required to be identified, and hence the
error correction frame 5 is configured and the frame
synchronization thereof is established independent of the
synchronization of the transmission frame 17.
Finally, referring to FIG. 10, description will be given of the
configuration of the error correction frame 5. In the motion video
data 3, corresponding to each block line as the encode unit, there
are arranged encoded data for a video frame the first block line
31, the second block line 32, . . . , and the n-th block line 33
located at the lowermost position in the screen, and the unique
word F.sub.s 30 identifying the division point of the video frame
is added at the top of the data, thereby forming the video frame
data 3. Next, subdividing the video frame data 3 from an arbitrary
bit position in a unit of 239 bits, a 1-bit error correction frame
bit S 34 and an error correction bit ECC 36 of the BCH code are
added to the 239-bit unit so as to constitute a 256-bit error
correction frame 5. Finally, the 16-phase interleave operation is
achieved in a unit of 16correction frames 5 excepting the frame bit
S 34, thereby forming the video data 7 to be multiplexed for a
generation of the transmission frame 17. In general, since the
amount of information of the video frame data 3 is not uniform for
each video frame, in order to match the amount of information with
the fixed code transmission speed, there is disposed the
transmission buffer 2 of FIG. 8 to effect the speed smoothing or
matching operation. However, since the capacity of the buffer
memory 2 is limited, there may possibly arise an overflow state and
an underflow state. In order to prevent such disadvantageous
states, according to the CCITT Draft Recommendation H.130 Part B,
there is introduced a control method, namely, the motion video
encoder 1 of FIG. 8 stops the encode operation when an overflow
occurs, whereas at an occurrence of an underflow state, the
pertinent information is forcibly generated by use of, for example,
the fixed-length encoding scheme. Furthermore, with consideration
of a delay of a response in the control method, the capacity of the
buffer memory is increased. The buffer memory occupancy is
restricted to be 180 kbits on the transmission side and 220 kbits
on the reception side, and the delay associated with the smoothing
operation is set to be a relatively large value of about 165
milliseconds (ms).
Since the conventional sub-rate multi-media data transmission
control system is configured as described above, there arise the
following problems, namely, the transmission frame synchronization
must be established independently of the error correction frame
synchronization, the size of the apparatus is increased, a long
period of time is required to establish all frame synchronizations
when the system is applied to the sub-rate ranging from 64 kbps to
384 kbps and hence a countermeasurement is necessary, the capacity
of the buffer memory is increased and the configuration of the
apparatus is accordingly complicated, and a greater amount of delay
occurs in the smoothing operation of the motion video data, which
causes a considerable hindrance in case of the sub-rate ranging
from 64 kbps to 384 kbps.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
sub-rate multi-media data transmission control system solving the
problems above in which synchronizations of the error correction
frame, the voice data frame, and the transmission frame can be
simultaneously established by use of a simple frame configuration
and the multi-media data at a sub-rate of 64 kbps.times.N.sub.1
(N.sub.1 is an integer exceeding 1) can be multiplexed with a
satisfactory matched operation.
Another object of the present invention is to provide a sub-rate
multi-media data transmission control system which can adaptively
effect a multiplexing operation with respect to the transmission
rate and the multiplex configuration so as to effectively utilize
transmission lines.
According to the present invention, there is provided a sub-rate
multi-media data transmission control system having a configuration
in which a multiplexing rate is adaptively assigned to a
transmission frame unit having a repeating cycle of 8 KHz; the
multiframe cycle, the error correction frame cycle, and the voice
data frame cycle are matched with each other; furthermore, the
motion video data packet is matched with the error correction frame
so as to adaptively transmit the video data frame and the dummy
data frame according to this unit of the frame.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be apparent from the following detailed
description taken in conjunction with the accompanying drawings in
which:
FIG. 1 is a configuration diagram schematically showing a sub-rate
multi-media data transmission control system according to an
embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating the configuration of a
transmission frame of the embodiment according to the present
invention;
FIG. 3 is an explanatory diagram useful to explain the
correspondence of the pertinent bit allocation or assignment in the
embodiment according to the present invention;
FIG. 4 is a schematic diagram illustrating the configurations of
the transmission frame, the FEC frame, and the video packet of the
embodiment according to the present invention;
FIG. 5 is an explanatory diagram useful to explain the
correspondence between the FEC frame and the ECC of the embodiment
according to the present invention;
FIG. 6 is an explanatory diagram useful to explain the
correspondence between the transmission frame and the voice data
frame of the embodiment according to the present invention;
FIG. 7 is an explanatory diagram useful to explain the
correspondence between the video frame and the video data packet of
the embodiment according to the present invention;
FIG. 8 is a configuration diagram schematically showing a
conventional sub-rate multi-media data transmission control system;
and
FIGS. 9-10 are explanatory diagrams useful to explain the
correspondence between the video frame and the error correction
frame according to the prior art system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIGS. 1-7, a description will be given of an
embodiment according to the present invention. The configuration of
FIG. 1 includes a motion video encoder 101, an error correction
encoder 102 for effecting, for example, the (640, 620, 5) shortened
BCH encoding on the encoded output delivered from the motion video
encoder 101, motion video data 103 outputted from the error
correction encoder 102, a voice encoder 104, a voice encoded data
105, for example, of 16/8 kbps, various external digital data 106,
an external data multiplexing section 107 which multiplexes the
external digital data 106 to attain external data of 8.times.m kbps
(m is an integer at least equal to one) by expanding the procedure,
for example, of the CCITT Recommendations X.50 control data 110
transmitted from a transmission control section 109 to a
communicating apparatus, a multiplexing section 111 which
adaptively multiplexes the motion video data, the voice data 105,
the external data 108, and the control data 110, a transmission
frame configure section 112 to form a transmission frame with a
variable transmission speed of 64/128 kbps, a control signal 113
outputted from the transmission controller 109 to control the
operation of the transmission frame configure section 112, a
control signal 114 delivered from the transmission controller 109
to control the operation of the error correction encoder 102, and a
transmission frame 115 outputted from the transmission frame
configure section 112 at a variable transmission speed of 64/128
kbps.
FIG. 2 is a diagram showing a transmission frame configuration in a
case where the transmission frame 115 of FIG. 1 can be changed over
between 64 kbps and 128 kbps in which the configuration includes a
transmission frame 120 having a frame repeating cycle of 8 KHz,
contents 121 of an odd-numbered frame corresponding to the #16 bit,
and contents 122 of an even-numbered frame associated with the #16
bit. The odd-numbered frame and the even-numbered frame constitute
a multiframe including, for example, 80 transmission frames.
FIG. 3 is a diagram illustrating a utilization example of
transmission frame format information BA contained in an area
ranging from the 17th frame to the 31st frame in the contents 121
of the odd-numbered frame corresponding to the #16 bit of FIG. 2.
The configuration includes transmission frame format information BA
(123) indicated in a unit of k multiframes (k is an integer at
least equal to one) and a transmission frame 124 of which the
format is changed after a delay of l multiframes with respect to
the transmission frame format BA 123.
FIG. 4 is a diagram showing the correspondence between the
transmission frame 120 of FIG. 2 and the FEC frame as a unit of the
(640, 620, 5) shortened BCH codes in which the configuration
includes an FEC frame structure 130 at a 128 kbps access, an FEC
frame structure 131 at a 64 kbps access, a fixed-length video data
packet 132 formed in a unit of the FEC frame, and a flag F.sub.f
133 indicating whether or not the motion video data channel 132 is
valid.
FIG. 5 is a diagram showing an example of transmission of an error
correction bit ECC of the (640, 620, 5) shortened BCH codes to be
transmitted depending on the contents 122 of the even-numbered
frame associated with the #16 bit of FIG. 2. The configuration
includes an error check bit ECC 140 to be sent in association with
each multiframe, an FEC frame 130 at a 128 kbps access, and an FEC
frame 131 at a 64 kbps access.
FIG. 6 is a diagram illustrating the correspondence between the
transmission frame 115 of FIG. 1 and the voice data frame, for
example, resulting from a 16/8 kbps high-performance encoding
operation. The configuration of FIG. 6 comprises, for example, a
320-bit voice frame 150 of 16 kbps and a 160-bit voice data frame
151 of 8 kbps.
FIG. 7 is a diagram showing the correspondence between the motion
video data frame and the motion video data packet 132 of FIG. 4.
The configuration includes a motion video data frame 160, underflow
data 161, a unique code word F.sub.s 162 indicating the top of a
video frame of the motion video data frame 160, a first data packet
163 following the unique code word F.sub.s, an intermediate data
packet 164, a final data packet 165, a dummy packet 166 indicating
underflow data 161, and an example 167 of a motion video data
packet 132 obtained by subdividing the motion video data frame
160.
Next, the operation of the configuration will be described. In FIG.
1, the encoded output delivered from the motion video encoder 10 is
smoothed with respect to the speed by means of the buffer memory,
the unique code word F.sub.s 162 indicating the top of the motion
video data frame and the flag F.sub.f 133 are added thereto, and
then the obtained data is sent to the error correction encoding
section 102 in a unit of the motion video data packet 132. The
error correction encoder 102 effects the (640, 620, 5) shortened
BCH encoding operation on the data in the unit of the motion video
data packet 132 in synchronism with the multiframe. In this
operation, the object of the BCH encoding includes only the bits of
the motion video data packet 132, namely, the bits assigned to the
other items are not encoded and are assumed to be, for example,
"1", thereby outputting the resultant data to the multiplexing
section 111. On the other hand, the encoded data 105 from the voice
encoder 104 is sent to the multiplexing section 111 by
synchronizing the multiframe with the voice data frames 150-151 at
a rate of 16/8 kbps. The external digital data 106 takes about
several minutes for a communication thereof when considering the
data of a facsimile, a personal computer, and the like. Only for
the communication, the external digital data 106 is multiplexed to
generate data of a rate=8 kbps.times.m (m is an integer at least
equal to one) according to the procedure, for example, conforming
to the CCITT Recommedations X.50 and the resultant data is then
delivered to the multiplexer 111. In the multiplexer 111, the data
is multiplexed into a transmission frame 115 of a rate of 64/128
kbps through the bit interleave scheme for each subchannel of 8
kbps which is a rate assigned to a bit of the transmission frame
115, and the resultant frame is then sent to a transmission line.
In this operation, the bit allocation or assignment information,
the error correction code ECC 140 of the BCH code, and the control
data 110 from the transmission controller 109 are multiplexed into
the frame bits 121-122 of the transmission frame 115, thereby
transmitting the resultant data to the transmission path in a
realtime operation. The transmission control section 109
supervising the communication control processing supplies the error
correction encode section 102 with the control signal 114
controlling the encode object bits, sends the control signal 113
controlling the transmission rate to the transmission frame
configure section 112, and accomplishes communications of the
control data 110 with a communicating apparatus.
Referring now to FIG. 2, description will be given of a
transmission frame configuration which can be changed over between
64 kbps and 128 kbps. First, assume that the bit speed is fixed to
128 kbps and that a transmission frame 120 includes two octets=16
bits. The transmission frame repeating cycle is obtained as 128
kpbs/16 bits=8 KHz and the bit rate assigned to a bit of a
transmission frame is expressed as 1 bit.times.8 KHz=8 kbps. At the
128 kbps access, the two octets of a transmission frame are
entirely used. On the other hand, at the 64 kbps access, only the
second octet of a transmission frame is utilized, namely, the first
octet is dummy and hence is not used. This utilization method is
enabled if the octet synchronization is guaranteed in the
transmission line. Next, the last bit #16 of the second octet is
assigned as the frame bit and this utilization is repeated in an
interval of 80 frames. A multiframe is defined to include 80
frames, which are then classified into even-numbered frames and
odd-numbered frames. In the frame bits 1-15 of an odd-numbered
frame, eight bits are assigned for a frame synchronization pattern
FA, and in the frame bits 17-31, eight bits are assigned for the
bit assignment information BA. In the odd-numbered frame, the
remaining 24 bits of a field AC including frame bits 33-79 have a
capacity of 2400 bps and are assigned to the control data 110. In a
case where the transmission line is used with a higher performance
or in a sophisticated fashion, while the control data 110 is not
being transmitted, another information can be sent by use of the
field AC. Next, 20 bits in ECCl including the frame bits 2-40 of
the even-numbered frame are used to transmit 20 error correction
bits of the (640, 620, 5) shortened BCH codes, whereas 20 bits of
ECC2 including frame bits 42-80 thereof are assigned for a
transmission of 20 error correction bits only at the 128 kbps
access, and these 20 bits are assigned to the video data 103 at the
64 kbps access.
When allocating of data=8 kbps.times.l (l is an integer at least
equal to one) in the transmission frame, l bits need only be
assigned in the frame. For example, for the 16 kbps voice data, two
bits of the transmission frame 120 is assigned. The bit allocation
information BA 121 is transmitted by use of the BA 121 to the
reception side. The remaining bits excepting those required for the
items above are allocated for the video data 103. For example, in a
case 8 kbps and 8 Kbps are respectively assigned to the external
data and the voice data, the bit allocated to the motion video data
is 42 kbps at the 64 kbps access and 104 kbps at the 128 kbps
access.
Furthermore, even when the data access rate of an access from the
communicating apparatus is unknown, the synchronization of the
transmission frame 120 can be established, which enables it to
identify the data access rate of the communicating apparatus from
the bit allocate information BA 121. Since the octet timing is
supplied from the transmission path, quite a short period of time
is necessary to establish the synchronization of the transmission
frame.
Referring now to FIG. 3, a description will be given of an example
of a dynamic adaptive bit allocation according to the bit allocate
information BA 121. It is beforehand assumed that the cycle k (k is
an integer at least equal to one) of the bit allocation is
determined, that a super frame is defined to include k multiframes,
and that the bit allocation is varied in a unit of the super frame.
For the synchronization of the super frame, a bit of the frame
synchronization pattern FA 121 of FIG. 2 is allocated. As a result,
the frame format information to be transmitted depending of the bit
allocate information BA 121 is sent in advance in time by a cycle,
namely, by k multiframes as compared with the transmission format
124 actually assigned. Consequently, an influence becomes greater
when a transmission line error occurs with respect to the bit
allocate information BA 121, and hence the same information is
successively transmitted k times, thereby effecting a
countermeasurement to judge the validity depending on the majority
rule.
Referring here to FIG. 4, a description will be given of an example
of the correspondence between the transmission frame 115 and the
FEC frame as a unit of the (640, 620, 5) shortened BCH encoding
operation. Since the number of frames of a multiframe=80 frames,
115 is 640 and 1280 bits respectively at the 64 kbps and 128 kbps
accesses, when effecting the 64 kbps and 128 kbps accesses to the
FEC frames with a length of 640 bits as a unit of the (640, 620, 5)
shortened BCH codes, an FEC frame 130 and two FEC frames 131 are
allocated, respectively. As a consequence, when the multiframe
synchronization is attained, the synchronization of the FEC frame
is automatically established. Next, the video data packet 132 is
defined to include the bits allocated to the motion video in the
FEC frame. The flag F.sub.f 133 indicating the presence/absence of
the filler is added as the first item to the motion video data
packet 132. Incidentally the utilization method of the flag F.sub.f
133 will be described later in this text. Assuming the number of
bits allocated to the other components to be N.sub.A (bits), the
number of bits of the video data packet 132 is represented as
640-N.sub.A (bits).
Referring now to FIG. 5, description will be given of the
correspondence between the FEC frames 130-131 and the error
Correction Code ECC 140 of the (640, 620, 5) shortened BCH codes,
the ECCs being distributed in the frame bits. The (640, 620, 5)
shortened BCH code is attained by reducing the (1023, 3) BCH code
by 383 bits and comprise 620 information bits and 20 error
correction bits ECC 140. The ECC 140 is transmitted with a delay in
time by an FEC frame as compared with the FEC frames 130-131. That
is, the ECC 140 associated with the previous frame is distributed
in the FEC frames 130-131, and the pertinent 20-bit ECC 140 does
not undergo the error correction encoding. This is also a
countermeasurement to prevent an uncorrectable error of an FEC
frame 130/131 from extending into the two FEC frames 130-131.
Furthermore, since an error processing is effected by another means
for bit information of the transmission frame 115 other than the
video data 103, the processing is accomplished on assumption that
the bits are to be "1".
In FIG. 6, for the 16 kbps voice data frame 150 and the 8 kbps
voice data frame 151, two bits and one bit are respectively
allocated for a frame at the 16 kbps and 8 kbps operations,
respectively, and the resultant data is interleaved for
transmission. On the other hand, also for the video data packet
132, the remaining bits of the transmission frame 115 are assigned
and are interleaved for transmission. As a result, the buffer
memory need only have a reduced capacity to effect the speed
conversion of the voice data 150-151.
Next, since the voice data frames 150-151 respectively associated
with 320 bits for 16 kbps and 160 bits for 8 kbps match with two
multiframes in the transmission frame 115, the synchronization can
be automatically established by attaining the matching with respect
to the cycle k of the bit allocate information 123, which enables
to effect, for example, a voice activation in this unit.
Referring now to FIG. 7, a description will be given of the
correspondence between the video data packet 132 of FIG. 4 and the
video data frame 160. A video frame 160 is subdivided (167) from an
arbitrary position thereof in a unit of the video data packet 132
and then the unique code word F.sub.s 162 is added as the first
item to the video data frame 160 for transmission. In this
operation, if the buffer memory of the motion video encoder 101 is
in the underflow state, the dummy 166 to be identified by the flag
F.sub.f 133 of FIG. 4 is transmitted in a unit of the video data
packet 132. However, at a transmission of the final data packet
165, after a video frame data is forcibly transmitted, the dummy is
added so as to configure a packet 132. The dummy can be identified
in association with the encode operation when the data is received.
As a result, the video image delay time at a low bit rate can be
reduced and the size of the send/receive buffer memories can be
minimized through an optimization of the capacity thereof, which
enables the efficient utilization of the transmission line.
Incidentally, although the error correction code ECC 122 is
distributed in the transmission frame bits in the embodiment above,
the ECC 122 may be arranged in the video data packet 132.
Furthermore, although the unique code word 162 is used to identify
the top of the video data frame 160 in the embodiment above, the
flag 133 in the video data packet 132 may be extended so as to
identify the first item, the intermediate item, the last item, and
the dummy of the motion video data frame 160 according to a unit of
the motion video data packet 132.
Moreover, although the 16/8 kbps voice data frames 150-151 are
described in conjunction with the embodiment above, the present
invention may also be applicable to other transmission speeds such
as 64 kbps.
In addition, although the 64/128 kbps accesses with variable rates
have been described for the embodiment above, even if the rate is
expressed as 64 kbps.times.N.sub.1 (N.sub.1 is an integer at least
equal to one), the transmission frame 115 need only be expanded in
a unit of the octet so as to attain the same effect as the
embodiment above.
Furthermore, although the embodiment has been described in case of
a transparent communication line, two 64 kbps lines may also be
used to obtain the same effect as the embodiment above.
Moreover, although the code length of the BCH code is fixed for
each multiframe in the embodiment described above, the code length
of the BCH code may be set to be identical to that of the video
data packet so as to change the word length depending on the number
of allocated bits, which also leads to the same effect as that of
the embodiment above.
According to configuration of the present invention, as described
above, bits are allocated for a unit of a transmission frame having
a frame cycle of 8 KHz, the multiframe cycle is matched with the
error correction frame and the voice data frame, the bit allocation
and access rate are adaptively variable based on the transmission
frame bits, and the video data frame is transmitted in a unit of
the video packet; consequently, an apparatus accessing the
communication route in a complicated fashion can be configured in a
simple structure. Moreover, there are attained effects, for
example, a movie image transmission can be implemented with a high
picture quality even through a low-bit-rate transmission line.
While the present invention has been described with reference to
the particular illustrative embodiments, it is not restricted by
those embodiments but only by the appended claims. It is to be
appreciated that those skilled in the art can change and modify the
embodiments without departing from the scope and spirit of the
present invention.
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